Rotational Sums

Each digit and the digit opposite it after a half turn add up to one of the listed totals.

Parameters

Maths

Class: first-order.

The shared predicates define the notation and every named predicate.

∀c ∈ C: D(c)+D(turn(c)) ∈ sums

Each cell digit and its half-turn counterpart sum to one of sums. The centre pairs with itself.

Example

---
format: open-rules
title: Rotational Sums example
setter: Example
source: ""
case: ""
library: https://rules.sudoku-sleuth.com/
status: read
---

```rules
sudoku 9x9
rotational-sums sums [10]
```

Satisfies the rule: r1c1=1, r9c9=9. The half-turn pair totals the allowed 10.

Breaks the rule: r1c1=2, r9c9=9. A half-turn pair has a different total.